JP2018141092A - Thermoplastic elastomer composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermoplastic elastomer composition for an airbag storage cover having excellent molded appearance, low temperature impact resistance and flexural modulus. A thermoplastic elastomer composition which is a dynamically heat-treated product of a mixture containing the following components (A) and (B) and a component (C) and a component (D). As the component (B), a saturated ethylene / α-olefin copolymer is particularly preferable, and an ethylene / 1-butene copolymer rubber is particularly preferable. Component (A): Polypropylene block copolymer component (B) having an ethylene unit content of 5 to 50% by mass: Ethylene / α-olefin copolymer component (C): Organic peroxide component (D): Crosslinking Auxiliary agent [selection diagram] None

Description

  The present invention relates to a thermoplastic elastomer composition capable of providing a molded article excellent in molding appearance, low-temperature impact resistance and flexural modulus, and an injection molded article comprising the thermoplastic elastomer composition, an automobile interior material, and an airbag storage Regarding the cover.

  An automobile air bag system is a system that protects a driver and a passenger in the event of a collision of an automobile, etc., and a collision detection device that detects an impact at the time of a collision, and an air bag according to the detection of the collision of the collision detection device. And an airbag device that operates to inflate the bag. The airbag device is installed in a steering wheel, an instrument panel in front of a passenger seat, a driver seat and a passenger seat, front and side pillars, and the like.

  Various proposals have been made regarding the structure and material of the airbag storage cover in the airbag apparatus so that the airbag storage cover can be cleaved as designed in a wide temperature range from low temperature to high temperature.

  Examples of the airbag storage cover made of olefinic thermoplastic elastomer include, for example, Patent Document 1, specific polypropylene polymer, ethylene / octene copolymer, styrene / conjugated diene block copolymer, and hydrocarbon rubber softener. Is disclosed which is made of a thermoplastic elastomer composition obtained by dynamic heat treatment in the presence of an organic peroxide. Patent Document 2 proposes a thermoplastic elastomer composition containing a specific amount of a propylene-based resin and a specific ethylene / α-olefin block copolymer.

International Publication No. 2006/070179 International Publication No. 2014/046139

In recent years, the flexibility of instrument panels due to the upgrading of automobiles has led to problems such as deformation of the airbag storage cover and instrument panel during deployment tests, and damage to the airbag storage cover at low temperatures due to improved airbag deployment output. There are concerns. In addition, the number of paintless airbag covers has been increasing to reduce manufacturing processes. From the above, for the airbag storage cover, flexural elasticity required as an airbag storage cover is required from the viewpoints of safety enhancement, design flexibility, and cost reduction by reducing the insert molding process of metal plate and nylon raw fabric. It is desired to improve appearance and low-temperature impact resistance while maintaining mechanical properties such as rate.
However, conventional materials for airbag storage covers have insufficient material strength, low-temperature impact resistance, and molded appearance.

  The problems to be solved by the present invention are a thermoplastic elastomer composition capable of obtaining a molded article excellent in molding appearance, low-temperature impact resistance and bending elastic modulus, and an injection molded article using this thermoplastic elastomer composition. Another object is to provide an automobile interior material and an airbag storage cover.

  As a result of intensive studies to solve the above problems, the inventor of the present invention converted a polypropylene block copolymer having a predetermined ethylene unit content and an ethylene / α-olefin copolymer into an organic peroxide and a crosslinking aid. The present inventors have found that a molded article excellent in molding appearance, low-temperature impact resistance and bending elastic modulus can be obtained from a thermoplastic elastomer composition obtained by dynamic heat treatment in the presence of the present invention, and the present invention has been achieved. That is, the gist of the present invention resides in the following [1] to [9].

[1] A thermoplastic elastomer composition which is a dynamic heat-treated product of a mixture containing the following component (A) and component (B) and component (C) and component (D).
Component (A): Polypropylene block copolymer component having an ethylene unit content of 5 to 50% by mass (B): Ethylene / α-olefin copolymer component (C): Organic peroxide component (D): Crosslinking Auxiliary

[2] The thermoplastic elastomer composition according to [1], wherein the component (B) is a saturated ethylene / α-olefin copolymer.

[3] The thermoplastic elastomer composition according to [1] or [2], wherein the α-olefin constituting the component (B) has 3 to 8 carbon atoms.

[4] The thermoplastic elastomer composition according to [3], wherein the component (B) is an ethylene / 1-butene copolymer rubber.

[5] The component (A) is contained in the polypropylene resin in the mixture in an amount of 50 to 100% by mass, and the component (B) is added to 10 parts with respect to 100 parts by mass in total of the polypropylene resin and the component (B). The heat according to any one of [1] to [4], comprising ~ 55 parts by mass, 0.01 to 0.8 parts by mass of component (C), and 0.01 to 1.8 parts by mass of component (D). Plastic elastomer composition.

[6] The thermoplastic elastomer composition according to any one of [1] to [5], which is an injection molding composition.

[7] An injection molded article of the thermoplastic elastomer composition according to any one of [1] to [6].

[8] An automobile interior material comprising the thermoplastic elastomer composition according to any one of [1] to [6].

[9] An airbag storage cover comprising the thermoplastic elastomer composition according to any one of [1] to [6].

  The injection-molded article, the automobile interior material, and the airbag storage cover of the present invention made of the thermoplastic elastomer composition of the present invention are excellent in molding appearance, low-temperature impact resistance and bending elastic modulus. For this reason, the airbag storage cover of this invention is excellent in durability, and can be used suitably also for a high output airbag.

  Hereinafter, the present invention will be described in detail, but the present invention is not limited to the following description, and can be arbitrarily modified and implemented without departing from the gist of the present invention. In addition, in this specification, when expressing by putting a numerical value or a physical-property value before and behind using "-", it shall use as what includes the value before and behind.

[Thermoplastic elastomer composition]
The thermoplastic elastomer composition of the present invention is a dynamic heat-treated product of a mixture containing the following component (A) and component (B), component (C) and component (D), and at least component (A) and component ( B) is obtained by dynamic heat treatment in the presence of component (C) and component (D).
Component (A): Polypropylene block copolymer component having an ethylene unit content of 5 to 50% by mass (B): Ethylene / α-olefin copolymer component (C): Organic peroxide component (D): Crosslinking Auxiliary

The airbag storage cover made of the thermoplastic elastomer composition of the present invention is excellent in low temperature impact resistance and good molded appearance while maintaining the original bending elastic modulus of the thermoplastic elastomer composition by the following mechanism. It has the feature.
Since the high-concentration ethylene component contained in the component (A) polypropylene block copolymer was copolymerized in the polymerization process, it was very finely dispersed. In the dynamic heat treatment, the ethylene / α-olefin of component (B) Highly compatible with the ethylene component of the copolymer, while being entangled with the ethylene / α-olefin copolymer, due to the molecular cutting effect of the organic peroxide of component (C) and the binding effect of the crosslinking aid of component (D) Due to the high dispersion effect, a fine and uniform sea-island structure of polypropylene matrix and rubber domain is formed.
However, when the ethylene / α-olefin copolymer of the component (B) is mainly an unsaturated ethylene / α-olefin copolymer, the crosslinked composition obtained by dynamic heat treatment has a highly reactive double bond. Therefore, it is preferable to use a saturated ethylene / α-olefin copolymer as the component (B) because the dispersibility is poor due to uneven crosslinking, and the molding appearance and low-temperature impact resistance tend to deteriorate. By using the ethylene / α-olefin copolymer, uniform dispersion can be obtained, and a molded article excellent in molding appearance and low-temperature impact resistance can be obtained. In particular, by using ethylene / 1-butene copolymer rubber, the comonomer branched chain is short, a more uniform dispersion can be obtained, and the low temperature impact resistance and the molded appearance can be improved.

<Component (A)>
The component (A) used in the thermoplastic elastomer composition of the present invention is a polypropylene block copolymer having an ethylene unit content of 5 to 50% by mass. In particular, the polypropylene block copolymer includes a propylene polymer component (A1) having a propylene unit content of 90 to 100% by mass and an ethylene / propylene copolymer having an ethylene unit content of 30 to 70% by mass. The ethylene unit in the polypropylene block copolymer comprising the polymer component (A2) and containing 30 to 80% by mass of the component (A1) with respect to the total amount of the component (A1) and the component (A2). The content of is preferably 5 to 50% by mass. Here, the content of the propylene unit in the component (A1) is a value when the total amount of all monomers constituting the component (A1) is 100% by mass, and the content of the ethylene unit in the component (A2) Is a value when the total amount of all monomers constituting the component (A2) is 100% by mass.

  In the component (A), the propylene-based polymer component (A1) is preferably a propylene homopolymer and a propylene / α-olefin copolymer as long as the propylene unit content is preferably 90 to 100% by mass. There may be. In the component (A), the propylene polymer component (A1) contributes to rigidity and heat resistance.

Specifically, the component (A1) is preferably a propylene homopolymer or a copolymer of propylene and at least one monomer selected from ethylene and an α-olefin having 4 to 10 carbon atoms. When component (A1) is a copolymer of propylene and ethylene and at least one monomer selected from ethylene and α-olefins having 4 to 10 carbon atoms, the monomer copolymerized with propylene is particularly ethylene, 1-butene. 1-hexene and 1-octene are preferred. In addition, these C4-C10 alpha olefins may use only 1 type, or may use 2 or more types.

  In the component (A), the ethylene / propylene copolymer component (A2) is an ethylene / propylene copolymer having an ethylene unit content of preferably 30 to 70% by mass. If it is in the range, an α-olefin other than propylene or a non-conjugated diene may be copolymerized. In the component (A), the propylene polymer component (A2) contributes to low temperature impact resistance. The ethylene unit content of the ethylene / propylene copolymer component (A2) is more preferably 35 to 65% by mass.

  In the component (A2), α-olefins other than propylene which may be copolymerized include 1-butene, 2-methylpropylene, 1-pentene, 3-methyl-1-butene, 1-hexene and 4-methyl. Examples include -1-pentene and 1-octene. In the component (A2), examples of the non-conjugated diene that may be copolymerized include 1,4-hexadiene, 1,6-octadiene, 2-methyl-1,5-hexadiene, and 6-methyl-1,5. -Chain non-conjugated dienes such as heptadiene, 7-methyl-1,6-octadiene; cyclohexadiene, dicyclopentadiene, methyltetrahydroindene, 5-vinylnorbornene, 5-ethylidene-2-norbornene, 5-methylene-2 Examples include cyclic non-conjugated dienes such as -norbornene, 5-isopropylidene-2-norbornene, and 6-chloromethyl-5-isopropenyl-2-norbornene.

  In the component (A), the content of the component (A1) is preferably 30 to 80% by mass with respect to the total amount of the component (A1) and the component (A2). When the content of the component (A1) is 30% by mass or more, rigidity is increased and heat resistance is maintained, and when the content of the component (A1) is 80% by mass or less, low-temperature impact resistance Will be held. From the viewpoint of further enhancing the effects of rigidity and heat resistance, the content of the component (A1) is more preferably 35% by mass or more. On the other hand, from the viewpoint of further enhancing the effect of low temperature impact resistance, the content of the component (A1) is more preferably 70% by mass or less, further preferably 60% by mass or less, and 50% by mass or less. It is particularly preferred.

  The polypropylene block copolymer of component (A) used in the present invention preferably has an ethylene unit content of 5 to 50% by mass, which is composed of the component (A1) and component (A2). When the content of the ethylene unit in the component (A) is 5% by mass or more, the dispersibility with the component (B) of the ethylene / α-copolymer is improved, and the appearance and the low-temperature impact resistance are excellent. If it is 50% by mass or less, it is excellent in rigidity and heat resistance. From this viewpoint, the content of the ethylene unit in the component (A) is preferably 6 to 45% by mass, and preferably 7 to 40% by mass. Moreover, it is still more preferable that it is 20-35 mass%. In addition, it is preferable that content of the propylene unit of a component (A) is 50-95 mass%, and it is more preferable that it is 60-93 mass%. Moreover, it is still more preferable that it is 65-80 mass%.

  Content of each component of a component (A1) in a component (A) and a component (A2) can be calculated | required as follows. That is, the component (A1) and the component (A2) are separated by the temperature rising elution fractionation method (TREF), and the content of the propylene unit and the content of the ethylene unit of the components (A1) and (A2) are determined by infrared spectroscopy. Find it. From these values, the ethylene unit content and the propylene unit content of the component (A) can also be determined.

  The melt flow rate (MFR) of the component (A) is not limited, but is usually 0.1 g / min or more, and preferably 0.2 g / 10 min or more, more preferably from the viewpoint of the appearance of the molded body. It is 0.3 g / 10 min or more, more preferably 0.4 g / 10 min or more. In addition, the melt flow rate (MFR) of the component (A) is usually 200 g / 10 min or less, and from the viewpoint of low temperature impact resistance, it is preferably 150 g / 10 min or less, more preferably 100 g / 10 min or less. It is. The MFR of component (A) is measured under the conditions of a measurement temperature of 230 ° C. and a measurement load of 21.18 N (2.16 kgf) according to JIS K7210 (1999).

  The method for producing the component (A) polypropylene block copolymer is not particularly limited. For example, a catalyst comprising an organoaluminum compound and a solid component comprising a titanium atom, a magnesium atom, a halogen atom, an electron donating compound and the like. A known multi-stage polymerization method using is used. The component (A1) is polymerized in the first step of the multistage polymerization method. Here, for example, a gas phase polymerization method, a solution polymerization method, or the like can be used. Subsequently, component (A2) is polymerized in the second step. Here, a gas phase polymerization method or the like can be used. As an example of such a multistage polymerization method, the manufacturing method described in Japanese translations of PCT publication No. 2004-536212 can be mentioned.

  Moreover, the component (A) used for the thermoplastic elastomer composition of the present invention may be a commercially available product. Examples of commercially available polypropylene block copolymers that can be used as the component (A) include Hifax CA138A and Adflex Q300F manufactured by LyondellBasel.

  As a component (A), only 1 type of said polypropylene block copolymer may be used, and 2 or more types of things with different physical properties, such as a monomer composition and MFR, may be mixed and used.

<Component (B)>
Component (B) used in the thermoplastic elastomer composition of the present invention is an ethylene / α-olefin copolymer.
As the α-olefin constituting the ethylene / α-olefin copolymer, 1-propylene, 1-butene, 2-methylpropylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl- 1-pentene, 1-octene and the like can be exemplified, but as described above, those having a short comonomer chain are preferable from the viewpoint of uniform dispersibility, and therefore 1-propylene, 1-butene, 1-hexene, 1 -The C3-C8 alpha olefin which has a carbon-carbon double bond in the terminal carbon atoms, such as octene, is preferable, and 1-butene is especially preferable. That is, the ethylene / α-olefin copolymer of component (B) is preferably an ethylene / 1-butene copolymer rubber. Only one type of α-olefin in the component (B) may be copolymerized with ethylene, or two or more types may be copolymerized with ethylene.

  As described above, when the component (B) has an unsaturated bond, the crosslinked structure formed by the dynamic heat treatment becomes non-uniform, so the component (B) is a saturated ethylene / α-olefin copolymer. Preferably there is. That is, it is preferable that a component (B) does not contain a diene component as a copolymerization component.

  The ethylene unit content of the component (B) ethylene / α-olefin copolymer is preferably 20% by mass or more and 80% by mass or less. The content of the ethylene unit of the component (B) is preferably larger in order to improve the low temperature impact property when the thermoplastic elastomer composition of the present invention is molded, and when the thermoplastic elastomer composition of the present invention is molded. From the viewpoint of the appearance, it is preferable that the amount is less. The content of the ethylene unit in the component (B) is more preferably 25 to 75% by mass, and further preferably 30 to 70% by mass.

  In addition, content of the ethylene unit in a component (B) and content of alpha-olefin units, such as 1-butene, can each be calculated | required by infrared spectroscopy.

  Although the melt flow rate (MFR) of the ethylene / α-olefin copolymer of the component (B) is not limited, it is usually less than 10 g / 10 min. From the viewpoint of strength, it is preferably 8 g / 10 min or less. Preferably it is 5 g / 10min or less, More preferably, it is 3 g / 10min or less. Further, the MFR of the component (B) is usually 0.01 g / 10 min or more, and from the viewpoint of fluidity, it is preferably 0.05 g / 10 min or more, more preferably 0.10 g / 10 min or more. is there. The MFR of component (B) is measured under the conditions of a measurement temperature of 190 ° C. and a measurement load of 21.18 N (2.16 kgf) according to JIS K7210 (1999).

Further, the density of the component (B) from the viewpoint of low-temperature impact resistance, and at 0.88 g / cm ³ or less, preferably 0.87 g / cm ³ or less. On the other hand, the lower limit is not particularly limited, but is 0.85 g / cm ³ or more. Although the density of a component (B) is a value measured based on JISK6760, a catalog value can also be employ | adopted about a commercial item.

  A known polymerization method using a known catalyst for olefin polymerization is used as a method for producing the ethylene / α-olefin copolymer of component (B). For example, as a catalyst for olefin polymerization, a Ziegler-Natta catalyst, a complex catalyst such as a metallocene complex or a nonmetallocene complex can be used, and as a polymerization method, a slurry polymerization method, a solution polymerization method, a bulk polymerization method, a gas polymerization method, Examples include a phase polymerization method. It is also possible to use commercially available products. Examples of commercially available products include Tafmer (registered trademark) manufactured by Mitsui Chemicals, Engage (registered trademark) manufactured by Dow Chemical.

  In the present invention, the ethylene / α-olefin copolymer as the component (B) may be used alone or in combination of two or more of those having different physical properties, types of copolymerization components, compositions and the like. .

<Ingredient (C)>
As the organic peroxide of component (C) used in the present invention, any of aromatic organic peroxides and aliphatic organic peroxides can be used. Specifically, di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl -2,5-di (t-butylperoxy) hexyne-3, 1,3-bis (t-butylperoxyisopropyl) benzene, 1,1-di (t-butylperoxy) -3,3,5 -Dialkyl peroxides such as trimethylcyclohexane; t-butylperoxybenzoate, t-butylperoxyisopropyl carbonate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,5-dimethyl-2 Peroxyesters such as, 5-di (benzoylperoxy) hexyne-3; acetyl peroxide, lauroyl peroxide, benzoy Peroxide, p- chlorobenzoyl peroxide, hydroperoxide, and the like, such as 2,4-dichlorobenzoyl peroxide and the like. Among these, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane is preferable. These organic peroxides may be used alone or in combination of two or more.

<Component (D)>
As the crosslinking aid of component (D) used in the present invention, compounds having N, N′-m-phenylene bismaleimide, toluylene bismaleimide, p-quinonedioxime, nitrobenzene, diphenylguanidine, trimethylolpropane, Polyfunctional vinyl compounds such as divinylbenzene, triallyl cyanurate, triallyl isocyanurate, diallyl phthalate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, trimethylolpropane tri ( Compounds having radical polymerizable carbon-carbon double bonds such as polyfunctional (meth) acrylate compounds such as meth) acrylate and allyl (meth) acrylate, and carbon straight chain of component (A) and / or component (B) Part of A compound having a functional group that reacts with the component can be used. These may be used alone or in combination of two or more.

<Ingredient (E)>
In the thermoplastic elastomer composition of the present invention, a polypropylene block copolymer not corresponding to component (A), that is, a polypropylene block copolymer having an ethylene unit content of less than 5% by mass is used as component (E). In addition, by using the component (E), it is possible to obtain the effect of improving the moldability and rigidity.

  The component (E) polypropylene block copolymer is the same as the component (E) polypropylene block copolymer except that the ethylene unit content is less than 5% by mass, preferably 2 to 4% by mass. A propylene-based polymer component (E1) having a propylene unit content of 90 to 100% by mass and an ethylene / propylene copolymer component having an ethylene unit content of 20 to 80% by mass is preferable. (E2), and preferably contains 90 to 98% by mass of component (E1) with respect to the total amount of component (E1) and component (E2). However, the content of the propylene unit in the component (E1) is a value when the total amount of all monomers constituting the component (E1) is 100% by mass, and the content of the ethylene unit in the component (E2) is It is a value when the total amount of all monomers constituting the component (E2) is 100% by mass.

  In the component (E), the propylene polymer component (E1) is a propylene homopolymer or a propylene / α-olefin copolymer as long as the propylene unit content is 90 to 100% by mass. Also good. In the component (E), the propylene polymer component (E1) contributes to rigidity and heat resistance.

Specifically, the component (E1) is preferably a propylene homopolymer or a copolymer of propylene and at least one monomer selected from ethylene and an α-olefin having 4 to 10 carbon atoms. When the component (E1) is a copolymer of propylene and ethylene and at least one monomer selected from ethylene and an α-olefin having 4 to 10 carbon atoms, the monomer copolymerized with propylene is particularly ethylene, 1-butene. 1-hexene and 1-octene are preferred. In addition, these C4-C10 alpha olefins may use only 1 type, or may use 2 or more types.

  In the component (E), the ethylene / propylene copolymer component (E2) is preferably an ethylene / propylene copolymer having an ethylene unit content of 20 to 80% by mass. If it is in the range, an α-olefin other than propylene or a non-conjugated diene may be copolymerized. In the component (E), the propylene polymer component (E2) contributes to low temperature impact resistance. In addition, content of the ethylene unit of a component (E2) becomes like this. More preferably, it is 30-70 mass%.

  In the component (E2), α-olefins other than propylene which may be copolymerized include 1-butene, 2-methylpropylene, 1-pentene, 3-methyl-1-butene, 1-hexene and 4-methyl. Examples include -1-pentene and 1-octene. In the component (E2), examples of the non-conjugated diene which may be copolymerized include 1,4-hexadiene, 1,6-octadiene, 2-methyl-1,5-hexadiene, and 6-methyl-1,5. -Chain non-conjugated dienes such as heptadiene, 7-methyl-1,6-octadiene; cyclohexadiene, dicyclopentadiene, methyltetrahydroindene, 5-vinylnorbornene, 5-ethylidene-2-norbornene, 5-methylene-2 Examples include cyclic non-conjugated dienes such as -norbornene, 5-isopropylidene-2-norbornene, and 6-chloromethyl-5-isopropenyl-2-norbornene.

  In the component (E), the content of the component (E1) is preferably 90 to 98% by mass with respect to the total amount of the component (E1) and the component (E2). When the content of the component (E1) is 90% by mass or more, rigidity is increased and heat resistance is maintained, and when the content of the component (E1) is 98% by mass or less, low-temperature impact resistance Will be held. From the viewpoint of further enhancing the effects of rigidity and heat resistance, the content of the component (E1) is preferably 92% by mass or more. On the other hand, from the viewpoint of further enhancing the effect of low-temperature impact resistance, the content of the component (E1) is preferably 97% by mass or less, and more preferably 96% by mass or less.

  In addition, content of each component of the component (E1) in a component (E) and a component (E2) can be calculated | required similarly to the component (A1) of a component (A), and a component (A2).

  The melt flow rate (MFR) of the component (E) is not limited, but is usually 0.1 g / min or more, and preferably 0.2 g / 10 min or more, more preferably from the viewpoint of the appearance of the molded body. Is 0.3 g / 10 min or more, more preferably 0.4 g / 10 min or more. The melt flow rate (MFR) of the component (E) is usually 200 g / 10 min or less, preferably 150 g / 10 min or less, and more preferably 100 g / 10 min from the viewpoint of low temperature impact resistance. It is as follows. The MFR of component (E) is measured under the conditions of a measurement temperature of 230 ° C. and a measurement load of 21.18 N (2.16 kgf) according to JIS K7210 (1999).

  Component (E) can also be produced in the same manner as component (A).

  In addition, as the component (E), a commercially available product can be used. Among commercially available polypropylene polymers, those that can be used as component (E) include Prime Polymer's Prime Polypro (registered trademark), Sumitomo Chemical's Sumitomo Noblen (registered trademark). ), Polypropylene block copolymer from Sun Allomer, Novatec (registered trademark) PP from Nippon Polypro, Molen (registered trademark) from LyondellBasel, ExxonMobil PP from ExxonMobil, Formolene (registered trademark) from Formosa Plastics, PP from Borales LG Chemical, SEETEC PP, A. Schulman's ASI POLYPROPYLENE, INEOS Olefins & Polymers, Inc. of INEOS PP, Braskem's Braskem PP, SAMSUNG TOTAL PETROCHEMICALS's Sumsung Total, Sabic's Sabic (registered trademark) PP, TOTAL PETROCHEMICALS company of TOTAL PETROCHEMICALS Polypropylene, SK Corporation of YUPLENE ( Registered trademark).

  As a component (E), only 1 type of said polypropylene block copolymer may be used, and 2 or more types of things with different physical properties, such as a monomer composition and MFR, may be mixed and used.

<Combination ratio>
The thermoplastic elastomer composition of the present invention is produced by subjecting components (A) to (D), a component (E) used as necessary, and a mixture of other components described later to dynamic heat treatment.

  As a ratio of each component in these mixtures to be subjected to dynamic heat treatment of each component, the component (A) is used so as to occupy 50 to 100% by mass with respect to the total polypropylene resin in the mixture, and in the mixture 10 to 55 parts by mass of component (B), 0.01 to 0.8 parts by mass of component (C), and component (D) with respect to 100 parts by mass of the total polypropylene resin and component (B). It is preferable to use 0.01 to 1.8 parts by mass. Other components will be described later.

  The component (B) of the ethylene / α-olefin copolymer by using the component (A) when the component (A) is 50% by mass or more based on the total polypropylene resin in the mixture subjected to the dynamic heat treatment. The appearance and low temperature impact characteristics due to the effect of improving the dispersion can be sufficiently obtained. From this viewpoint, the component (A) is preferably used in an amount of 55 to 100% by mass, particularly 60 to 100% by mass, based on the total polypropylene resin in the mixture.

  Component (B) is the total polypropylene resin in the mixture to be subjected to dynamic heat treatment (usually this total polypropylene resin is the sum of component (A) and component (E) used as necessary. ) And the component (B) are 10 parts by mass or more with respect to 100 parts by mass in total, and the effect of improving the appearance and low-temperature impact resistance by using the component (B) can be sufficiently obtained. When the content is less than or equal to part by mass, the content of the component (A) can be sufficiently ensured and the flexural modulus can be excellent. From this viewpoint, the component (B) is preferably used in an amount of 15 to 55 parts by mass with respect to a total of 100 parts by mass of the total polypropylene resin and the component (B) in the mixture.

  Component (C) is the total polypropylene resin in the mixture to be subjected to dynamic heat treatment (usually this total polypropylene resin is the sum of component (A) and component (E) used as necessary. ) And the component (B) are 0.01 parts by mass or more with respect to 100 parts by mass in total, and the effect of improving the appearance and low-temperature impact resistance is sufficiently obtained by forming a crosslinked structure by using the component (C). When the amount is 0.8 parts by mass or less, the crosslinking reaction can be sufficiently controlled. From this viewpoint, the component (C) is 0.02 to 0.5 parts by mass, particularly 0.03 to 0.3 parts by mass with respect to 100 parts by mass in total of the total polypropylene resin and the component (B) in the mixture. It is preferable to use parts.

  Component (D) is the total polypropylene resin in the mixture to be subjected to dynamic heat treatment (usually this total polypropylene resin is the sum of component (A) and component (E) used as necessary. ) And component (B) are 0.01 parts by mass or more with respect to 100 parts by mass in total, and the effect of improving low-temperature impact resistance and flexural modulus by forming a crosslinked structure by using component (D) Can be sufficiently obtained, and when it is 1.8 parts by mass or less, the crosslinking reaction can be sufficiently controlled. From this viewpoint, the component (D) is 0.02 to 1.5 parts by weight, particularly 0.05 to 1.0 parts by weight, based on a total of 100 parts by weight of the total polypropylene resin and the component (B) in the mixture. It is preferable to use parts.

<Other ingredients>
In addition to the components (A) to (E), the thermoplastic elastomer composition of the present invention includes the following additives and components (A) depending on various purposes within a range that does not significantly impair the effects of the present invention. , (B), (E) and other components such as resins and elastomers (hereinafter referred to as “other resins”) can be blended.

  Optional ingredients include colorants, antioxidants, heat stabilizers, light stabilizers, UV absorbers, neutralizers, lubricants, anti-clouding agents, anti-blocking agents, slip agents, flame retardants, dispersants, antistatic agents. And various additives such as conductivity imparting agent, metal deactivator, molecular weight modifier, antibacterial agent and fluorescent brightener. The amount of these additives is appropriately set according to the required characteristics. For example, the antioxidant is used in the range of 0.01 to 5 parts by mass per 100 parts by mass of the total amount of components (A) and (B) or components (A), (B) and (E).

  Other resins that can be contained in the thermoplastic elastomer composition of the present invention include polyethylene resins other than components (A), (B), and (E), polyolefin resins such as polypropylene resins, styrene thermoplastic elastomers, Examples include polyester resins, polyamide resins, styrene resins, acrylic resins, polycarbonate resins, polyvinyl chloride resins, and various other elastomers. Other resins mentioned above may contain only one type or two or more types. In the case of using a styrene thermoplastic elastomer, it is preferable to further use a hydrocarbon rubber softener.

  However, when the thermoplastic elastomer composition of the present invention contains the above-mentioned other resins and elastomers, the content of the thermoplastic elastomer composition of the present invention having components (A) to (D) as essential components. In order to effectively obtain the effects, the components (A) and (B) or the components (A), (B) and (E) are combined in 100 parts by mass from the viewpoints of appearance, low temperature impact resistance, rigidity and mechanical strength. The amount is preferably 10 parts by mass or less.

<Method for producing thermoplastic elastomer composition>
The thermoplastic elastomer composition of the present invention comprises a raw material mixture containing the above components (A) to (D) or components (A) to (E) and other components used as necessary in a predetermined ratio. It is obtained by dynamic heat treatment.

  In the present invention, “dynamic heat treatment” means kneading in the molten state or semi-molten state in the presence of the component (C) and the component (D). This dynamic heat treatment is preferably carried out by melt kneading. As a mixing and kneading apparatus therefor, for example, a non-open Banbury mixer, a mixing roll, a kneader, a twin screw extruder, or the like is used. Among these, it is preferable to use a twin screw extruder. As a preferable aspect of the manufacturing method using this twin-screw extruder, each component is supplied to the raw material supply port (hopper) of the twin-screw extruder which has a some raw material supply port, and dynamic heat processing is performed.

  The temperature at which the dynamic heat treatment is performed is usually 80 to 300 ° C, preferably 100 to 250 ° C. Moreover, the time which performs dynamic heat processing is 0.1 to 30 minutes normally.

<Physical properties>
The thermoplastic elastomer of the present invention is obtained by subjecting the component (A), (B) or component (A), (B), (E) to dynamic heat treatment in the presence of the component (C) and the component (D). Thus, it is excellent in molding appearance, low temperature impact resistance, bending elastic modulus and the like.

(Charpy impact strength)
In the present invention, the failure type of the notched Charpy impact test at a temperature of −40 ° C. in accordance with JIS K7111 is used as an index of low temperature impact resistance.
C: Complete destruction (In which the specimen breaks into two or more pieces)
H: Hinge failure (incomplete failure where only a thin hinge-like surface layer with low bending strength becomes a specimen that cannot be separated together)
P: Partial failure (incomplete failure that does not meet the definition of hinge failure)
N: Undestructed The destruction type of the Charpy impact test of the thermoplastic elastomer composition of the present invention is preferably H or more, more preferably P or more, and further preferably NB.

(Flexural modulus)
The thermoplastic elastomer composition of the present invention preferably has a flexural modulus of 600 MPa or less, particularly 200 to 550 MPa, measured according to JIS K7203. If the flexural modulus of the thermoplastic elastomer composition is larger than the above upper limit, the low-temperature impact resistance tends to decrease, and if it is smaller than the lower limit, the rigidity and strength tend to be insufficient.

<Molding method>
The thermoplastic elastomer composition of the present invention can be molded by a known method as required and used as various molded products. Examples of the molding method include molding methods usually used for thermoplastic elastomers, such as injection molding, extrusion molding, hollow molding, compression molding, and the molding methods mentioned in the section of the airbag storage cover below. Can be mentioned. Moreover, you may perform secondary processes, such as lamination molding and thermoforming, after that. The thermoplastic elastomer composition of the present invention may be formed as a single body or may be combined with other materials to form a laminate.

[Airbag storage cover]
Using the thermoplastic elastomer composition of the present invention, generally, using a normal injection molding method, or various molding methods such as a gas injection molding method, an injection compression molding method, and a short shot foam molding method, if necessary. By using a molded body, it can be used as an airbag storage cover. In particular, the molding conditions for injection molding the airbag storage cover are as follows.

  The molding temperature when the airbag housing cover is injection-molded is usually 150 to 300 ° C, preferably 180 to 280 ° C. The injection pressure is usually 5 to 100 MPa, preferably 10 to 80 MPa. The mold temperature is usually 0 to 80 ° C, preferably 20 to 60 ° C.

  The airbag storage cover of the present invention obtained by molding the thermoplastic elastomer composition of the present invention operates when a high-speed moving body such as an automobile senses its impact or deformation when a collision accident occurs, Used as an airbag storage cover of an airbag system that protects an occupant by inflating and deploying.

[Automobile interior materials]
Using the thermoplastic elastomer composition of the present invention, an automotive interior material such as an instrument panel, a front pillar trim, a door trim, a shift lever, various consoles, and a skin material for a headlining is formed by an extrusion molding method or an injection molding method. be able to.

The molding temperature at the time of extruding the automobile interior material is usually 150 to 250 ° C, preferably 170 to 220 ° C. Moreover, the molding temperature at the time of press molding is usually 150 to 250 ° C, preferably 190 to 240 ° C.
The molding conditions for injection molding the automobile interior material are the same as the injection molding conditions for the airbag storage cover.

  The automobile interior material obtained by molding the thermoplastic elastomer composition of the present invention sufficiently satisfies the required characteristics such as durability, low temperature impact resistance and appearance.

  EXAMPLES Hereinafter, although the content of this invention is demonstrated more concretely using an Example, this invention is not limited by a following example, unless the summary is exceeded. The values of various production conditions and evaluation results in the following examples have meanings as preferred values of the upper limit or lower limit in the embodiments of the present invention, and preferred ranges are the above-described upper limit or lower limit values and the following values: It may be a range defined by a combination of values of the examples or values of the examples.

[material]
<Component (A)>
(A-1) Polypropylene block copolymer Hifax CA138A manufactured by LyondellBasel:
Content of ethylene unit: 28% by mass
MFR (: 230 ° C., load 21.18 N): 2.6 g / 10 min Propylene polymer component (A1) (Propylene unit content: 100% by mass)
Content: 42% by mass
Content of ethylene / propylene copolymer component (A2) (ethylene unit content: 48 mass%, propylene unit content: 52 mass%): 56 mass%
Melting temperature: 160 ° C

(A-2): Polypropylene block copolymer (obtained by polymerizing a propylene homopolymer in the first step and then polymerizing an ethylene / propylene copolymer in the second step)
Content of ethylene unit: 8% by mass
MFR (230 ° C., load 21.18 N): 2.5 g / 10 min

<Component (B)>
(B-1): Tuffmer (registered trademark) A0550S manufactured by Mitsui Chemicals, Inc.
Ethylene / 1-butene copolymer rubber Density: 0.86 g / cm ³
MFR (190 ° C., load 21.18 N): 0.5 g / 10 min Mooney viscosity ML1 + 4 (100 ° C.): 65

(B-2): Engage (registered trademark) 8150 manufactured by Dow Chemical Company
Ethylene / 1-octene copolymer rubber Ethylene unit content: 39% by mass
Density: 0.86 g / cm ³
MFR (190 ° C., load 21.18 N): 0.5 g / 10 min Mooney viscosity ML1 + 4 (121 ° C.): 33

<Ingredient (C)>
(C-1): Kayahexa (registered trademark) AD40C manufactured by Kayaku Akzo Corporation
A mixture of 40% by mass of 2,5-dimethyl-2,5-di (t-butylperoxy) hexane and 60% by mass of calcium carbonate

<Component (D)>
(D-1): Mixture of 60% by weight divinylbenzene and 40% ethylvinylbenzene

<Ingredient (E)>
(E-1): Polypropylene block copolymer (obtained by polymerizing a propylene homopolymer in the first step and then polymerizing an ethylene / propylene copolymer in the second step)
Content of ethylene unit: 4% by mass
MFR (230 ° C., load 21.18 N): 60 g / 10 minutes

[Evaluation method]
1) External appearance of injection-molded body Using the obtained thermoplastic elastomer composition, an injection pressure of 50 MPa, a cylinder temperature of 220 ° C., and a mold temperature of 40 ° C. are produced by an in-line screw type injection molding machine (“IS130” manufactured by Toshiba Machine Co., Ltd.). Then, a sheet having a thickness of 3 mm, a width of 100 mm, and a length of 400 mm was formed, and the appearance of the obtained molded sheet was visually confirmed. Those having no flow mark were evaluated as having excellent molded appearance.

2) Flexural modulus (unit: MPa)
Using the resulting thermoplastic elastomer composition, the flexural modulus was measured with an inline screw type injection molding machine (“IS130” manufactured by Toshiba Machine Co., Ltd.) at an injection pressure of 50 MPa, a cylinder temperature of 220 ° C., and a mold temperature of 40 ° C. The test piece (thickness 4 mm × width 10 mm × length 90 mm) was molded, and the flexural modulus of this test piece was measured according to JIS K7203 at a span of 64 mm and a bending speed of 2 mm / min. It was measured. The flexural modulus is preferably in the range of 200 to 600 MPa.

3) Low temperature impact resistance (Charpy impact test fracture state)
Using the obtained thermoplastic elastomer composition, Charpy impact strength was measured at an injection pressure of 50 MPa, a cylinder temperature of 220 ° C., and a mold temperature of 40 ° C. with an in-line screw type injection molding machine (“IS130” manufactured by Toshiba Machine Co., Ltd.). A test piece (4 mm thick with a notch × 12.7 mm wide × 64 mm long test piece) was molded. The obtained test piece was subjected to a Charpy impact test at a temperature of −40 ° C. according to JIS K7111, and the fracture type of the Charpy impact test was used as an index of low-temperature impact resistance.
C: Complete destruction (test specimen breaks into two or more pieces)
H: Hinge fracture (incomplete fracture where only the hinge-like thin surface layer with low bending strength becomes a specimen that cannot be separated together)
P: Partial failure (incomplete failure that does not meet the definition of hinge failure)
N: Undestructed The destruction type of the Charpy impact test of the thermoplastic elastomer composition of the present invention is preferably H or more, more preferably P or more.

[Example / Comparative Example]
<Example 1>
(A-1) 50 parts by mass, (b-1) 30 parts by mass, (c-1) 0.05 parts by mass, (d-1) 0.1 parts by mass, (e-1) 20 parts by mass, oxidation 0.1 parts by weight of an inhibitor (trade name Irganox (registered trademark) 1010, manufactured by BASF Japan) was blended for 1 minute in a Henschel mixer, and the same direction twin screw extruder (“TEX30α” manufactured by Kobe Steel), L / D = 45, the number of cylinder blocks = 13) at a rate of 20 kg / h, the temperature was raised in the range of 180 to 210 ° C., and melt kneading was performed to produce pellets of a thermoplastic elastomer composition. Evaluation of said 1) -3) was performed about the pellet of the obtained thermoplastic elastomer composition. The evaluation results are shown in Table 1.

<Examples 2-9 and Comparative Examples 1-5>
Except for blending the resin components shown in Table 1, pellets of a thermoplastic elastomer composition were obtained in the same manner as in Example 1, and the evaluations 1) to 3) were performed in the same manner as in Example 1. The evaluation results are shown in Table 1.

From Table 1, according to the thermoplastic elastomer composition of the present invention obtained by dynamic heat treatment of component (A) and component (B) in the presence of component (C) and component (D), the molded appearance and It can be seen that a molded article having excellent bending elastic modulus and good low-temperature impact resistance can be obtained.
On the other hand, in Comparative Example 1 that does not contain the component (A), the molded appearance is poor and the low-temperature impact resistance is also poor. In Comparative Example 2 using only the component (A) and Comparative Example 3 not using the component (D), the molding appearance and the low-temperature impact resistance are inferior. The comparative example 4 which does not use a component (C) and the comparative example 5 which does not use a component (C) and a component (D) have a bad shaping | molding external appearance.

  The thermoplastic elastomer composition of the present invention is excellent in molding appearance, low temperature impact resistance, bending elastic modulus and the like, and is very useful as a molding material for airbag storage covers, automobile interior materials and the like.

Claims (9)

A thermoplastic elastomer composition which is a dynamic heat-treated product of a mixture containing the following component (A) and component (B) and component (C) and component (D).
Component (A): Polypropylene block copolymer component having an ethylene unit content of 5 to 50% by mass (B): Ethylene / α-olefin copolymer component (C): Organic peroxide component (D): Crosslinking Auxiliary   The thermoplastic elastomer composition according to claim 1, wherein the component (B) is a saturated ethylene / α-olefin copolymer.   The thermoplastic elastomer composition according to claim 1 or 2, wherein the α-olefin constituting the component (B) has 3 to 8 carbon atoms.   The thermoplastic elastomer composition according to claim 3, wherein component (B) is an ethylene / 1-butene copolymer rubber.   The component (A) is contained in the polypropylene resin in the mixture in an amount of 50 to 100% by mass, and the component (B) is added in an amount of 10 to 55% by mass with respect to 100 parts by mass in total of the polypropylene resin and the component (B). The thermoplastic elastomer composition according to any one of claims 1 to 4, comprising 0.01 to 0.8 parts by mass of component (C) and 0.01 to 1.8 parts by mass of component (D). object.   The thermoplastic elastomer composition according to any one of claims 1 to 5, which is an injection molding composition.   An injection-molded body of the thermoplastic elastomer composition according to any one of claims 1 to 6.   An automobile interior material comprising the thermoplastic elastomer composition according to any one of claims 1 to 6.   An airbag storage cover comprising the thermoplastic elastomer composition according to any one of claims 1 to 6.